Hi all,
This reply is to the previous three posts, as some possibilities are raised more than once. Thanks for all the help...

Temp space - checked that, and there's plenty of room. Helpfully enough, we did have some trouble with space limitations on /var/tmp on this server previously, and the error messages were fairly explicit.

Output space - same thing, there's plenty of room in the output directory.

Path to "sort" - a good point; I hadn't tried using the full path to the binary. But the script works perfectly until I increase the number of data files I'm processing past a certain point (3 of them). So I doubt the path is a problem.

Unnecessary "cat" - oops. Quite right. I honestly don't know why I put that in there! I'll try it without "cat" - could that extra process be using up all our allocated memory? Again, I still don't understand why I wouldn't get some kind of error, if that were the case.

Here's another interesting wrinkle. Before and after the "sort" system call, I just tried putting some other system calls to see if they worked. So now it looks like this:

system("echo 'now executing sort...' ");
system(" cat $file | sort -t\\| +1 -2 > $file.out");
system("ls -la");
[download]

If I process 2 data files, all 3 system calls execute. If I process 3 data files, the first 2 system calls execute, but the third one doesn't. If I process 4 data files, none of them execute. Spooky! So, okay, if I'm running out of memory, why do the system calls die so silently? I guess I'm probably trying to determine if this is a Perl thing, or a Solaris thing. I'm baffled, though, because I've always found Perl to have exceptionally useful errors. I'll toss it by the Unix admins just to see what happens....
Thanks!